Natural products in green tea have attracted a great deal of attention because of anti-oxidant and anti-cancer activity (“Chemoprotection: A Review of the potential therapeutic antioxidant properties of green tea (Camellia sinensis) and certain of its constituents” Mitscher, L. A.; Jung, M.; Shankel, D.; Dou, J. H.; Steele, L.; Pillai, S. P Medicinal Research Reviews, 17(4), 327, 1997). The anti-oxidant and anti-cancer activity is believed to be due to flavonoids or catechin phenolic antioxidants. The major catechins in green tea are (−)-epicatechin, (+)-catechin, (−)-catechin, (−)-epicatechin gallate, (−)-epigallocatechin gallate (EGCG) and (−)-epigallocatechin.
Recent studies have revealed that the naturally occurring catechins can inhibit some forms of breast cancer cell proliferation (“Estrogen receptor-mediated actions of polyphenolic catechins in vivo and in vitro” Goodin, M G.; Fertuck, K. C.; Zacharewski T. R.; Rosengren, R. J” Toxicological sciences, 69(2), 354, 2002) and tumor growth and prevent recurrence in some forms of Stage I-II breast cancer in women (Green tea polyphenols and cancer chemoprevention: multiple mechanisms and endpoints for Phase II Trials Moyers, S. B.; Kumar, N. B. Nutrition reviews, 62(5), 204, 2004).
Naturally occurring green tea catechins have also been used as chemopreventive agents for skin cancer (“Cutaneous photochemoprotection by green tea: A brief review” Ahmad, N.; Mukhtar, H. Skin Pharmacol Appl Skin Physiol, 14(2), 69, 2001), against colon cancer (“Green tea constituent (−)-epigallocatechin-3-gallate inhibits topoisomerase I activity in human colon carcinoma cells” Berger, S. J.; Gupta, S.; Belfi, C. A.; Gosky, D. M.; Mukhtar, H Biochemical and Biophysical Research Communications, 288(1), 101, 2001) and are believed to reduce the risk of cancer of the pancreas, rectum (“Green tea consumption and the risk of pancreatic and colorectal cancers” Ji, B. T.; Chow, W. H.; Hsing, A. W.; McLaughlin, J. K.; Dai. Q.; Gao, Y. T.; Blot, W. J.; Fraumeni, J. F Jr Int. J. Cancer, 70(3), 255, 1997) and lungs (“Cancer inhibition by green tea” Fujiki, H.; Suganuma, M.; Okabe, S.; Sueoka, N.; Komori, A.; Sueoka, E.; Kozu, T.; Tada, Y.; Suga, K.; Imai, K.; Nakachi, Kei Mutation Research, 402, 307, 1998). These flavonoids have also found to possess other desirable properties such as anti-inflammatory, antiallergic, antithrombotic and antiviral properties (“Flavonoids as anti-cancer agents: Structure-Activity Relationship study” Lopez-Lazaro, M.; Curr. Med. Chem.—Anti-Cancer Agents, 2, 691, 2002).
In particular, EGCG has been shown to have pleotrophic effects in the inhibition of tumor angiogenesis and the prevention of cancer metastasis by interfering with proteases, urokinase and matrix metalloproteinase (MMP) activation, as well as direct inhibition of MMP secretion by tumor cells (Demeule, M., Michaud-Levesque, J., Annabi, B., Gingras, D., Boivin, D., Jodoin, J. Lamy, S., Bertrand, Y. and Beliveau, R. “Green Tea Catechins as Novel Antitumor and Antiangiogenic Compounds” Curr. Med. Chem.—Anti-Cancer Agents, 2002, 2, 441-463).
Naturally occurring flavanoids have also been evaluated for effects against cardiac damage, viral infection, and obesity (Suzuki J, Ogawa M, Sagesaka Y M, Isobe M. 2005. Catechins attenuate myocardial cell infiltration and fibrosis but do not prolong graft survival in murine cardiac allografts. Transplant Proc. January-February; 37(1):119-20; Liu S, Lu H, Zhao Q, He Y, Niu J, Debnath A K, Wu S, Jiang S. 2005. Theaflavin derivatives in black tea and catechin derivatives in green tea inhibit HIV-1 entry by targeting gp41. Biochim Biophys Acta. April 6; Wolfram S, Raederstorff D, Wang Y, Teixeira S R, Elste V, Weber P. 2005. TEAVIGO (Epigallocatechin Gallate) Supplementation Prevents Obesity in Rodents by Reducing Adipose Tissue Mass. Ann Nutr Metab. 49(1):54-63).
However, there are major disadvantages to the use of naturally occurring flavanoids such as EGCG. For example, it is known to be highly unstable in the vehicles used to solubilize it, such as ethanol or dimethyl sulfoxide (DMSO), losing activity within hours. Moreover, EGCG must typically be used at concentrations of 5-40 μg/mL to maintain activity, and is typically not at doses of 0.1 μg/mL.
Oligomerization of catechins has been reported to significantly enhance their anti-oxidant activity (Kurisawa, M.; Chung, J. E.; Kim, Y. J.; Uyama, H; Kobayashi, S. “Amplification of antioxidant activity and Xanthine Oxidase Inhibition of Catechin by enzymatic polymerization” Biomacromol., 2003, 4(3), 469-471). However these oligomerized forms of catechins are partly insoluble, which limits effective delivery into biological systems. Moreover, without purification from their reaction mixtures, they can be incompatible with biological systems. As the need for new and effective pharmaceuticals continues to grow, there is also concern over the environmental impact of toxic starting materials, intermediates, byproducts, solvents, and the like in the synthesis of new pharmaceuticals, which can also impair the biocompatibility, requiring additional purification.
Therefore, there is a need in the art for new methods of synthesizing biocompatible, soluble catechins that have improved biological activity. Moreover there is a need for methods of synthesizing these agents that is simple and environmentally benign.